An aryloxy-acetic acid derivative belonging to the class of loop diuretics. Ethacrynic acid interferes with the chloride binding site of the Na+, K+, Cl- cotransporter system in the thick ascending loop of Henle, thereby inhibiting the reabsorption of sodium, potassium, and chloride ions. This leads to an increase in the excretion of sodium, potassium, chloride, calcium, and water.